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H Pashler

Publications and source records attributed to H Pashler.

At least 19 recordsLinked to original sources
PubMed2001

Attention and performance.

Recent progress in the study of attention and performance is discussed, focusing on the nature of attentional control and the effects of practice. Generally speaking, the effects of mental set are proving more pervasive than was previously suspected, whereas automaticity is proving less robust. Stimulus attributes (e.g. onsets, transients) thought to have a "wired-in" ability to capture attention automatically have been shown to capture attention only as a consequence of voluntarily adopted task sets. Recent research suggests that practice does not have as dramatic effects as is commonly believed. While it may turn out that some mental operations are automatized in the strongest sense, this may be uncommon. Recent work on task switching is also described; optimal engagement in a task set is proving to be intimately tied to learning operations triggered by the actual performance of a new task, not merely the anticipation of such performance.

Attention↗
PubMed2000

Evidence for split attentional foci.

A partial report procedure was used to test the ability of observers to split attention over noncontiguous locations. Observers reported the identity of 2 targets that appeared within a 5 x 5 stimulus array, and cues (validity = 80%) informed them of the 2 most likely target locations. On invalid trials, 1 of the targets appeared directly in between the cued locations. Experiments 1, 1a, and 2 showed a strong accuracy advantage at cued locations compared with intervening ones. This effect was larger when the cues were arranged horizontally rather than vertically. Experiment 3 suggests that this effect of cue orientation reflects an advantage for processing targets that appear in different hemifields. Experiments 4 and 4a suggest that the primary mechanism supporting the flexible deployment of spatial attention is the suppression of interference from stimuli at unattended locations.

Adult↗
PubMed2000

How persuasive is a good fit? A comment on theory testing.

Quantitative theories with free parameters often gain credence when they closely fit data. This is a mistake. A good fit reveals nothing about the flexibility of the theory (how much it cannot fit), the variability of the data (how firmly the data rule out what the theory cannot fit), or the likelihood of other outcomes (perhaps the theory could have fit any plausible result), and a reader needs all 3 pieces of information to decide how much the fit should increase belief in the theory. The use of good fits as evidence is not supported by philosophers of science nor by the history of psychology; there seem to be no examples of a theory supported mainly by good fits that has led to demonstrable progress. A better way to test a theory with free parameters is to determine how the theory constrains possible outcomes (i.e., what it predicts), assess how firmly actual outcomes agree with those constraints, and determine if plausible alternative outcomes would have been inconsistent with the theory, allowing for the variability of the data.

Humans↗
PubMed2000

The role of iconic memory in change-detection tasks.

In three experiments, subjects attempted to detect the change of a single item in a visually presented array of items. Subjects' ability to detect a change was greatly reduced if a blank interstimulus interval (ISI) was inserted between the original array and an array in which one item had changed ('change blindness'). However, change detection improved when the location of the change was cued during the blank ISI. This suggests that people represent more information of a scene than change blindness might suggest. We test two possible hypotheses why, in the absence of a cue, this representation fails to produce good change detection. The first claims that the intervening events employed to create change blindness result in multiple neural transients which co-occur with the to-be-detected change. Poor detection rates occur because a serial search of all the transient locations is required to detect the change, during which time the representation of the original scene fades. The second claims that the occurrence of the second frame overwrites the representation of the first frame, unless that information is insulated against overwriting by attention. The results support the second hypothesis. We conclude that people may have a fairly rich visual representation of a scene while the scene is present, but fail to detect changes because they lack the ability to simultaneously represent two complete visual representations.

Cues↗
PubMed1999

Visual selection mediated by location: feature-based selection of noncontiguous locations.

Experiments using two different methods and three types of stimuli tested whether stimuli at non-adjacent locations could be selected simultaneously. In one set of experiments, subjects attended to red digits presented in multiple frames with green digits. Accuracy was no better when red digits appeared successively than when pairs of red digits occurred simultaneously, implying allocation of attention to the two locations simultaneously. Different tasks involving oriented grating stimuli produced the same result. The final experiment demonstrated split attention with an array of spatial probes. When the probe at one of two target locations was correctly reported, the probe at the other target location was more often reported correctly than were any of the probes at distractor locations, including those between the targets. Together, these experiments provide strong converging evidence that when two targets are easily discriminated from distractors by a basic property, spatial attention can be split across both locations.

Choice Behavior↗
PubMed1998

When two memories can and cannot be retrieved concurrently.

We examined whether two memories can be retrieved concurrently from long-term memory. In Experiment 1, the subjects recalled words, either from two categories--alternating between the two--or from just one category. In Experiment 2, the subjects recalled two words belonging to either the same category or different categories, and the category prompts for these two responses appeared either simultaneously or successively. The results of both studies are consistent with the view that two items from different categories must be retrieved serially, whereas two items from the same category can be retrieved in parallel.

Adult↗
PubMed1995

Does perceptual analysis continue during selection and production of a speeded response?

This study asked whether perceptual analysis of a stimulus can continue while a response to this stimulus is being generated. In Experiment 1, subjects rapidly named a word that was visually degraded with superimposed pixels. Near the time of response, degradation was removed for a short time and then followed by a mask. Subjects then made a second, unspeeded judgment about the identity of the word. Unspeeded judgments were more accurate, showing that the degradation-free stimulus exposure was processed. In Experiment 2, the task was the same, but the degradation was gradually faded out for an individually adjusted duration. Comparison of unspeeded-response accuracy on trials with and without a speeded response showed that stimulus analysis continued at full efficiency during speeded-response generation. The results support conclusions of Rabbit and Vyas (1981) that perceptual analysis continues during response stages. This form of continuous processing does not necessarily contradict discrete stage models of human information processing, however.

Adult↗
PubMed1995

Spatial attention and vernier acuity.

This study examined whether or not vernier acuity would be improved if the location of a briefly presented vernier stimulus was pre-cued. The vernier target appeared alone, or together with straight lines or ellipses. Effects of spatial pre-cuing were found only when straight line distractors were present. It is suggested that since the straight lines are confusable with the vernier targets, they introduce statistical noise in decision. Precuing the most probable location that contains a target may help by allowing this noise to be excluded.

Attention↗
PubMed1995

Repetition blindness: perception or memory failure?

Repetition blindness (RB) is the failure to report a repeated item when reporting all of the elements from a rapidly displayed sequence of visually presented items. N. Kanwisher (1987) has characterized RB as a perceptual problem. Experiments 1 and 4 manipulated the order of report of the repeated items. Experiments 2-4 employed tasks other than full report that should still have shown RB according to a perceptual hypothesis, but none was found. In Experiment 5, RB was found when one of the repetitions was spoken and the other was presented visually; this RB could be localized to retrieval processes. RB appears to reflect processes and strategies peculiar to full report from rapid displays rather than any fundamental perceptual limitation and might be the same as the Ranschburg effect found in immediate recall tasks.

Humans↗
PubMed1995

Attentional limits in memory retrieval.

The hypothesis that episodic memory retrieval can occur in parallel with other cognitive processes was tested in 2 experiments. Participants memorized words and then performed speeded cued recall (Experiment 1) or speeded yes-no recognition (Experiment 2) in a dual-task situation. The psychological refractory period design was used: The participant was presented with a single test item at various stimulus onset asynchronies (SOAs; 50-1,200 ms) after a tone was presented in an auditory-manual 2-alternative choice reaction task. Reducing the SOA increased the memory task reaction times. This slowing was additive with the effect of variables slowing retrieval in the memory task. The results indicate that memory retrieval is delayed by central processes in the choice task, arguing that the central bottleneck responsible for dual-task interference encompasses memory retrieval as well as response selection.

Adult↗
PubMed1995

Visual selection mediated by location: selecting successive visual objects.

In these experiments, each stimulus consists of a series of frames, each containing a target digit of one color and a distractor digit of another color. The task is to name the highest digit of the target color. Subjects make fewer errors when successive targets appear at the same location than when they appear at different locations, apparently because they select target objects by using a mechanism that is based on location. When successive targets appear at the same location, there is no need to "move" the selection mechanism to a new location, leaving more time to identify the stimuli. These experiments show that location-based selection is used even though selection by color would be more direct. They also demonstrated a method of measuring location-based selection that can be applied to a variety of visual tasks. Further experiments reveal that although location-based selection is used to identify a digit in the presence of a digit distractor, it is not used to identify a digit in the presence of a letter distractor, suggesting that this selection mechanism is not used in this situation to prevent interference among the basic features making up letters and digits, but to inhibit responses associated with the distractors.

Adult↗
PubMed1994

Sequential operation of disconnected cerebral hemispheres in split-brain patients.

When two concurrent sensorimotor tasks require separate responses, selection of the first response generally delays selection of the second. Dual-task performance was examined in four patients who had undergone surgical transection of the forebrain commissures including the corpus callosum. One light flash was presented to each visual field in succession, and patients made a choice response to each stimulus with the ipsilateral hand, thereby confining the tasks to separate hemispheres. All four showed dual-task interference very similar to that found with normal individuals. Therefore, still-intact subcortical structures must play a critical role in sequencing response selection processes (the 'dual-task bottleneck'), confirming the distinction between the attentional limitations involved in planning actions and those involved in perceptual analysis.

Brain↗
PubMed1994

Graded capacity-sharing in dual-task interference?

Research suggests that dual-task interference is caused by a central bottleneck (together with response grouping and impaired preparation). The emphasis placed on the 1st response in these experiments, however, may have discouraged the sharing of processing resources between tasks. In the present experiment, instructions placed equal emphasis on 2 choice reaction-time tasks in which stimuli were presented simultaneously on 20% of the trials. In contrast to a graded trade-off of resources, a bottleneck predicts bimodality in the distribution of interresponse intervals for the 2 tasks, reflecting the 2 possible orders in which their respective central stages might be performed. Most subjects showed such a bimodality, along with other signs of a bottleneck; the remainder showed evidence of response grouping. The data suggest that the bottleneck is structural rather than strategic and make the graded sharing of resources less plausible.

Attention↗
PubMed1994

Dual-task interference in simple tasks: data and theory.

People often have trouble performing 2 relatively simple tasks concurrently. The causes of this interference and its implications for the nature of attentional limitations have been controversial for 40 years, but recent experimental findings are beginning to provide some answers. Studies of the psychological refractory period effect indicate a stubborn bottleneck encompassing the process of choosing actions and probably memory retrieval generally, together with certain other cognitive operations. Other limitations associated with task preparation, sensory-perceptual processes, and timing can generate additional and distinct forms of interference. These conclusions challenge widely accepted ideas about attentional resources and probe reaction time methodologies. They also suggest new ways of thinking about continuous dual-task performance, effects of extraneous stimulation (e.g., stop signals), and automaticity. Implications for higher mental processes are discussed.

Attention↗
PubMed1994

Overlapping mental operations in serial performance with preview.

Dual-task research has revealed a response-selection bottleneck: response selection cannot occur simultaneously in two different tasks, though perceptual processing may overlap response selection (Welford, 1952; Pashler & Johnston, 1989). In serial performance with preview, the same task is performed repeatedly, but stimuli are available well before response. Does the dual-task bottleneck limit the rate of responding in this situation, despite the fact that task set need not change? Four experiments examined manual responses to letters, varying stimulus preview. Preview increased RTs for the first response and reduce the subsequent inter-response intervals (IRIs). Preview also reduced the effect of visual intensity and response duration on IRIs, whereas effects of stimulus-response mapping variables were unchanged. These results indicate that the response-selection bottleneck limits serial performance, just as it limits concurrent performance of two unrelated tasks. This implies that the response-selection bottleneck is not caused by the need to switch task set.

Adult↗
PubMed1993

Saccadic eye movements and dual-task interference.

Four dual-task experiments required a speeded manual choice response to a tone in a close temporal proximity to a saccadic eye movement task. In Experiment 1, subjects made a saccade towards a single transient; in Experiment 2, a red and a green colour patch were presented to left and right, and the saccade was to which ever patch was the pre-specified target colour. There was some slowing of the eye movement, but neither task combination showed typical dual-task interference (the "psychological refractory effect"). However, more interference was observed when the direction of the saccade depended on whether a central colour patch was red or green, or when the saccade was directed towards the numerically higher of two large digits presented to the left and the right. Experiment 5 examined a vocal second task, for comparison. The findings might reflect the fact that eye movements can be directed by two separate brain systems--the superior colliculus and the frontal eye fields; commands from the latter but not the former may be delayed by simultaneous unrelated sensorimotor tasks.

Attention↗
PubMed1993

Dual-task interference and the cerebral hemispheres.

It has been argued that dual-task interference is reduced when the two cerebral hemispheres can carry out the two tasks independently. Evidence for this idea has arisen from studies involving manipulations such as lateralized stimulation or response, or requiring mental operations believed to depend primarily on a particular hemisphere. However, these studies have typically involved a very limited degree of response uncertainty, which appears critical in producing the most extreme dual-task interference (the psychological refractory effect). Pairs of tasks with independent response uncertainty were examined, and various manipulations were used to promote hemispheric task separation. Dual-task interference was not modulated by these manipulations. It seems likely that response selection represents a central bottleneck, in the sense that this process cannot operate simultaneously and independently in the two hemispheres.

Adult↗